Scared might be having a miscarriage

I am two and a half weeks late on af took pregnancy test frst week positive. Now I am having very dark spotting yesterday afternoon when I went to pee then stopped. Same this morning frst pee dark red then alil brown discharge. Went to the hospital yesterday they said they got a pos pregnancy test but nothing on ultrasound wait to days they'll test hcg levels again to see if they are rising. I'm super nervous. Has this happened to anyone before and they were fine???